Thin film transistor-liquid crystal display (TFT-LCD) technology is mainly classified into a Twisted Nematic (TN) mode and a wide viewing angle mode. In a TN mode TFT-LCD, electrodes on two sides of a liquid crystal layer are located on a color filter substrate and an array substrate, respectively, and are in a plane, respectively; the structures of the color filter substrate and the array substrate in the TN mode are also relatively simple. The wide viewing angle mode includes a transverse electric field display technology, such as an In-panel Switching (IPS) mode, in which a more reasonable plane electric field can be fowled through combination of transparent finger-like electrodes, and the arrangement of liquid crystal molecules is optimized; and moreover, because the transparent electrodes are used in place of opaque metal electrodes, transmissivity are remarkably increased.
The structure of a conventional array substrate in the IPS wide viewing angle mode is shown in FIG. 1. The array substrate comprises: a plurality of gate lines 1, a plurality of data lines 2 and at least one common electrode line 15. The common electrode line 15 is parallel to the data lines 2. The plurality of gate lines 1 and the plurality of data lines 2 intersect each other to define a plurality of pixel units, each of which comprises a thin film transistor as a switching element, a pixel electrode 3 and a common electrode 6, and the thin film transistor is connected to the pixel electrode 5. The thin film transistor comprises a gate electrode 11, a source electrode 12, a drain electrode 13 and a semiconductor channel 3. A terminal of the common electrode 6 for pixel units in a row is electrically connected to the common electrode line 15 via a via hole 41 over the common electrode 15. A via hole 4 for electric connection to a driving circuit and so on is formed in an insulating layer over a terminal of a gate line 1. Within each of the pixel units, the pixel electrode 5 and the common electrode 6 both are comb-like electrodes, their finger parts are interdigitated, and an electric field for driving liquid crystals is formed when electricity is applied across the electrodes.
For the array substrate in the wide viewing angle mode, because the interval between the pixel electrode and the common electrode is too small, a tiny offset between two layers of electrode may cause difference in capacitance between the pixel electrode and the common electrode, thereby giving rise to a problem that the display picture is non-uniform (Mura).
FIG. 2 is a structurally schematic view showing a conventional array substrate in the IPS wide viewing angle mode when a pixel electrode 5 and a common electrode 6 are dislocated. As shown in FIG. 2, within one pixel unit, a finger part of the common electrode 6 is shifted to the right with respect to a finger part of the pixel electrode 5.